What it means
U0100 — Lost communication with ECM/PCM 'A'. BeeEmUu groups this code under Network with a severity of Stop / drive carefully.
Code
U0100SystemNetwork
SeverityStop / drive carefully
FormatSAE J2012
Provenance
The title and severity above are seeded from the open-research source of record: https://www.sae.org/standards/content/j2012_202104/. BeeEmUu stores short factual descriptions only; no proprietary ISTA or OEM text is reproduced.
Related schematics
- e90-cas3-pinout — PT-CAN timeout — first place to inspect: splice at CAS pin 16/17 after rodent damage in engine bay.
Community repair opinions
No community opinion file exists for this code yet. Add one by opening a PR with community/opinions/U0100.toml.
Frequently asked
Is code U0100 safe to clear?
Clearing is only safe once you have read and recorded the freeze frame. Re-appearing after a clear is the useful signal; clearing without recording destroys it.
Is U0100 a BMW-specific or a generic code?
This is a generic SAE J2012 code, so any OBD-II tool can read it.